The present invention is generally directed to medical (and in many cases, more specifically to neurological) treatment devices, systems, and methods. In exemplary embodiments, the invention provides radiosurgical treatment methods and systems for directing ionizing radiation toward a target tissue within a brain of a patient so as to treat psychiatric conditions, and particularly to treat anxiety disorders (such as Post-Traumatic Stress Disorder (PTSD), Generalized Anxiety Disorder (GAD), Panic Disorder, Social Phobia, Specific Phobia, and the like). The dose of radiation will generally be sub-lethal so that the tissue within the target need not undergo frank cell death, with efficacy often instead being provided via radiomodulation of neural activity.
Behavioral disorders, also known as “psychiatric disorders” and “functional disorders,” are neurologic and psychiatric conditions that stem from defective regulation of certain brain regions. Patients that suffer from behavioral disorders often exhibit abnormal neural activity along a particular neural circuit within the brain. Typically, areas within the neural circuits of the brain of a behavioral disorder patient are either over-active or under-active, even though the cells of the tissue appear histologically normal. This class of pathology contrasts with structural disorders, in which there is something morphologically or identifiably and physically abnormal with a tissue, such as an injury or a cancerous tumor. Nonetheless, the impact of behavioral disorders, including depression, OCD, addiction, and the like, can be devastating on the lives of patients and their families.
In neurology and psychiatry, behavioral disorders are most often treated with medications. Unfortunately, these medications are often not effective, and can often be non-specific as to where they exert effects within the body. Hence, medications for treatment of behavioral disorders often produce undesirable side effects.
Attempts are being made to treat behavioral disorders by surgical implantation of treatment devices. These surgical implants typically include stimulating electrodes driven by a pacemaker-like pulse generator unit. For example, abnormal neuronal activity associated with intractable depression may be inhibited by continuously applying localized electrical current using a process called deep brain stimulation. Unfortunately, deep brain stimulation generally involves the invasive placement of electrodes into deep brain structures, along with the subcutaneous implantation of an electrical generator with batteries. Such approaches, however, are expensive, and are generally accompanied by risks associated with the surgery, particularly with the risks associated with surgically accessing and/or violating tissues of the brain for implantation of the electrodes such as bleeding and infection. These approaches can also suffer from device-related risks, including device failure, battery-life limits, and the like.
A variety of both historical and modern techniques seek to treat patients by effectively killing cells within selected areas of the brain. Surgical techniques have been developed that intentionally kill or ablate specific regions of the brain using a variety of devices and energy forms. For example, radiation is a widely used method for inducing cell death and effectively destroying tissue within the brain. Radiation is primarily applied to tissues of the brain to treat benign and malignant tumors. The clinical practice of irradiation to produce selective cell death and/or stop growth in tumors generally makes use of computerized systems that seek to minimize injury to adjacent normal anatomy. The biologic effects of radiation can be dose and volume dependent, and are largely ascribed to lethal chromosomal injury which results in disruption of the normal cell cycle. Non-chromosomal, i.e. epigenetic, pathways of cell injury are also believed to play a role in cellular death under some circumstances. Even lower doses of ionizing radiation can induce epigenetic changes that permanently or semi-permanently alter tissue function in the absence of cell death.
While inducing necrosis of selected tissues of the brain can be well worthwhile to halt growth of a malignant tumor or the like, there can be significant and even debilitating side effects, particularly when the tissues targeted for treatment are associated with higher cognitive functions. For example, targeting of apparently healthy tissues of the hyperactive or hypersensitive neural circuits associated with depression, addiction, OCD, or other behavioral disorders with cellularly lethal doses of radiation might effectively treat the disorder, but may significantly degrade cognitive abilities, induce neurological side-effects, and impact quality of life of the patient.
In addition to currently recognized neural circuits associated with behavioral disorders, there is an increasing awareness that abnormal neural activity within the neural circuits of the brain may be associated with a variety of deleterious behavior patterns. For example, while obesity is not uniformly recognized as a class of psychiatric behavioral disorder, there is increasing understanding that hyperphagia (excessive appetite and consumption of food) can be associated with excessive activity in an associated neural circuit. Similar deleterious behavior patterns and their associated anatomical structures within the brain are likely to be identified in the future.
In light of the above, it has recently been proposed to treat behavioral disorders, obesity, and the like by irradiating neural tissues of the circuits associated with those disorders with sub-lethal doses of radiation so as to modulate the activity of those circuits. These proposed therapies present tremendous advantageous, but as with many exciting advancements, still further innovations would be beneficial. Specifically, Post Traumatic Stress Disorder (PTSD) and other anxiety disorders have received more and more clinical attention in recent years. The effects of these anxiety disorders may range widely, and a number of alternative therapies that have been proposed has been expanding. Nonetheless, the individuals with these conditions continue to suffer, even when their behavior remains within societal norms. Hence, it would be desirable if new treatment techniques could be developed help mitigate the debilitating effects of anxiety disorders without imposing excessive surgical trauma on the patient, without subjecting the patient to drug regiments and/or having to damage or kill neural tissues that result in loss of significant cognitive, emotional, or physical functionality to the patient. It would be particularly desirable if these benefits could be provided at reasonable costs by modifying existing treatment infrastructure and technologies.